Various operation detection sensors which detect an operation onto an operation surface by the operator have been contrived. Although the operation detection sensors are of the electrostatic capacity type, the thermal resistance type, the piezoelectric acoustic type, and the infrared sensor type, it is necessary to mount a different displacement detection sensor for detecting the amount of displacement orthogonal to the operation surface at pressing the operation surface.
Patent Literature 1 describes a touch input device having a touch panel as an operation detection sensor, and a pressure-sensitive sensor detecting pressing onto an operation surface. In the touch input device of Patent Literature 1, the pressure-sensitive sensor is arranged on the lower face of the touch panel (the face on the opposite side of the operation surface), and has the same area as the touch panel. In addition, in the touch input device of Patent Literature 1, a protective layer is arranged on the touch panel on the operation surface side.
Patent Literature 2 describes an operation input device in which electrodes in a matrix are formed on both faces of a planar piezoelectric substance.
Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. H5-61592
Patent Literature 2: Japanese Patent Application Laid-Open (JP-A) No. 2006-163618
However, in the structures of the conventional techniques, the following problems arise.
In the touch input device described in Patent Literature 1, the pressure-sensitive sensor senses pressing onto the operation surface by the operator through the protective film and the touch panel. Consequently, the pressing detection sensitivity is low. Further, when the touch input device is mounted in a mobile terminal, the member having predetermined rigidity and made of glass is typically mounted on the operation surface. In this case, the pressing detection sensitivity lowers.
In the operation input device described in Patent Literature 2, the linear electrodes in a matrix detect electric charge generated by pressing, with the result that the pressing detection sensitivity is low. Further, when the operation input device is mounted in a mobile terminal, the member having predetermined rigidity and made of glass is typically mounted on the operation surface. In this case, like the operation input device described in Patent Literature 1, the pressing detection sensitivity lowers.